阅读说明：本技术 一种屈服强度550MPa级热镀锌钢板及其生产方法 (Hot-dip galvanized steel plate with yield strength of 550MPa and production method thereof ) 是由 王占业 王滕 李雄杰 杨平 孙霖 李伟刚 张百勇 李超 周红兵 张喜秋 何峰 于 2020-07-08 设计创作，主要内容包括：本发明公开了一种屈服强度550MPa级热镀锌钢板及其生产方法,属于金属材料技术领域。本发明的热镀锌钢板化学成分重量百分比为：C 0.006％～0.010％、Si≤0.01％、Mn 0.10～0.30、P≤0.015％、S≤0.040％、Als 0.005％～0.070％、Ti 0.001％～0.080％、Nb 0.001％～0.060％、N≤0.0030％、O≤0.0020％、Cu 0.030％～0.060％、Cr 0.010％～0.040％,其余为铁和其他杂质。通过控制钢板中C元素含量,并添加Mn、Cr、Al、Cu等元素,并对添加元素的含量进行控制,提高钢的强度。还在钢中添加Ti和Nb,并使两种元素含量满足公式0.050％≤Ti+Nb≤0.120％。两种元素既可提高强度,又使韧性变好,是最经济、最有效改善钢性能的方法。通过两种元素的复配,能够进一步的细化铁素体晶粒尺寸,同时提高钢板的强度和韧性,使钢的强度和韧性能够良好的匹配,同时满足屈服强度和延伸率的要求。(The invention discloses a hot-dip galvanized steel plate with a yield strength of 550MPa and a production method thereof, belonging to the technical field of metal materials. The hot dip galvanized steel sheet comprises the following chemical components in percentage by weight: 0.006-0.010% of C, less than or equal to 0.01% of Si, 0.10-0.30% of Mn, less than or equal to 0.015% of P, less than or equal to 0.040% of S, 0.005-0.070% of Als, 0.001-0.080% of Ti, 0.001-0.060% of Nb, less than or equal to 0.0030% of N, less than or equal to 0.0020% of O, 0.030-0.060% of Cu, 0.010-0.040% of Cr, and the balance of iron and other impurities. The strength of the steel is improved by controlling the content of C element in the steel plate, adding Mn, Cr, Al, Cu and other elements and controlling the content of the added elements. Ti and Nb are also added into the steel, and the contents of the two elements meet the formula of 0.050 percent to 0.120 percent. The two elements can improve the strength and the toughness, and are the most economical and effective method for improving the performance of the steel. By compounding the two elements, the ferrite grain size can be further refined, the strength and the toughness of the steel plate can be improved, the strength and the toughness of the steel can be well matched, and the requirements of yield strength and elongation are met.)

1. A hot dip galvanized steel sheet with the yield strength of 550MPa is characterized in that: the hot dip galvanized steel sheet comprises the following chemical components in percentage by weight: 0.006-0.010% of C, less than or equal to 0.01% of Si, 0.10-0.30% of Mn, less than or equal to 0.015% of P, less than or equal to 0.040% of S, 0.005-0.070% of Als, 0.001-0.080% of Ti, 0.001-0.060% of Nb, less than or equal to 0.0030% of N, less than or equal to 0.0020% of O, 0.030-0.060% of Cu, 0.010-0.040% of Cr, and the balance of iron and other impurities.

2. The hot-dip galvanized steel sheet with a yield strength of 550MPa according to claim 1, wherein: the chemical component proportion of the hot dip galvanized steel sheet meets the formula: ti + Nb is more than or equal to 0.050% and less than or equal to 0.120%.

3. A method for producing a hot-dip galvanized steel sheet according to claim 1 or 2, characterized by comprising the steps of:

firstly, pretreating molten iron;

step two, smelting in a converter and finely adjusting the alloy;

step three, refining in an RH furnace;

step four, continuous casting;

step five, hot rolling and cold rolling;

and step six, galvanizing.

4. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 3, characterized by comprising the following steps: in the first step, the pretreated molten iron is controlled to have the element S less than or equal to 0.0015 percent and the slag-removing bright surface more than or equal to 80 percent.

5. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 4, characterized by comprising the following steps: in the second step, alloy auxiliary materials are added in sequence during tapping: pre-deoxidizing carbon powder, high-carbon ferromanganese, carburant, slag charge and aluminum iron, and deoxidizing the steel; and meanwhile, slag is blocked, and slag discharging and rephosphorization are prevented.

6. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 5, characterized by comprising the following steps: in the third step, RH adopts a light treatment process, and oxygen is blown in the early and middle stages according to the temperature and the oxygen level; and ensuring that the net circulation time is not less than 6min before breaking.

7. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 6, characterized by comprising the following steps: in the fourth step, the molten steel is calmed for not less than 20min, and the flow of argon blown by the stopper rod is controlled to be 4-6 NL/min; the target temperature of the tundish is controlled to be 15-30 ℃ above the liquidus temperature; casting at constant drawing speed under dynamic soft pressure, and controlling the fluctuation range of the liquid level within +/-3 mm; the discharging temperature of the casting blank is controlled to be 1200-1230 ℃.

8. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 7, characterized by comprising the following steps: in the fifth step, high-pressure descaling is carried out on an outlet and an inlet of the hot rolling rough rolling, an edge heater is arranged on an inlet of the hot rolling finish rolling, and high-pressure descaling water is fully opened at an outlet and an inlet of the finish rolling; the finishing temperature is controlled to be 870-910 ℃; the coiling temperature is controlled to be 580-630 ℃; the total rolling reduction rate of cold rolling is controlled to be 80-95 percent.

9. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 8, characterized by comprising the following steps: in the sixth step, the annealing temperature T and the time T of the RTF section are controlled to satisfy a relation of T/100 and 100/T being equal to or less than 4, and the finishing elongation L1 and the withdrawal and straightening elongation L2 are controlled to satisfy a relation of L1+ L2 being equal to or more than 0.6% and equal to or less than 1.2%.

10. The method for producing the hot-dip galvanized steel sheet with the yield strength of 550MPa according to claim 9, characterized by comprising the following steps: the annealing temperature of the RTF section is controlled to be 600-630 ℃, and the time is 20-50 s; the finishing elongation L1 is controlled to be 0.5-1.0%, and the withdrawal and straightening elongation L2 is controlled to be 0.1-0.5%.

Technical Field

The invention relates to the technical field of metal materials, in particular to a hot-dip galvanized steel plate with a yield strength of 550MPa and a production method thereof.

Background

Galvanized steel sheets are welded steel sheets having a hot-dip or electro-galvanized layer on the surface thereof, and are widely used in the construction, home appliances, vehicles and ships, container manufacturing, electro-mechanical industry, and the like. The production and processing methods can be divided into the following categories: (1) a hot dip galvanized steel sheet, which is a steel sheet having a zinc layer adhered to the surface thereof by dipping the steel sheet into a molten zinc bath. (2) The galvannealed steel sheet is similarly produced by a hot dip method, and is immediately heated to about 500 ℃ after being taken out of the bath, thereby forming an alloy thin film of zinc and iron. (3) And (3) electroplating the zinc steel plate. (4) Single-sided and double-sided differentially galvanized steel sheets. (5) Alloy and composite galvanized steel sheet.

The high-strength hot-dip galvanized steel sheet can be applied to the automobile household appliance structural parts and the building industry, the strength of the steel sheet is improved, the steel sheet is thinned through improving the strength, the weight of the steel sheet can be reduced, the cost of a final product is reduced, and meanwhile, the safety level is improved. The high toughness of the steel plate can improve the processing performance and the fatigue resistance of products, the service life of the steel plate is prolonged, and the steel plate gradually develops towards high strength and high toughness along with the improvement of the safety level requirement. However, the existing galvanized steel sheet can only improve one aspect of the performance, and when the strength of the steel sheet is improved, the elongation rate is reduced; when the elongation rate meets the requirement, the strength of the steel cannot meet the requirement. Meanwhile, when the existing galvanized steel sheet is produced, the strength of the steel sheet often generates large fluctuation, so that the product output is unstable, and the cost is increased.

Through retrieval, the Chinese patent application number: ZL201710994660.X, the application date is 10 and 23 months in 2017, and the invention name is as follows: the hot-dip aluminum-zinc steel plate for the 550 Mpa-level structure and the preparation method thereof relate to the chemical components of the hot-dip aluminum-zinc steel plate of the application as follows: 0.02-0.07% of C, less than or equal to 0.03% of Si, 0.15-0.30% of Mn, less than or equal to 0.020% of P, less than or equal to 0.020% of S, 0.015-0.035% of Nbs, 0.020-0.070% of Als, and the balance of Fe and inevitable impurities. The preparation method is to perform cold rolling by adopting a low cold rolling reduction rate of 55-65%. The obtained steel plate has excellent mechanical properties, the yield strength is more than 550MPa, the tensile strength is more than 560MPa, and the elongation A80 is about 10%. However, the hot-dip aluminum-zinc plated steel sheet of the application adopts low carbon components, and the Nb strengthening improves the strength, resulting in a low elongation.

Authorization notice number: CN102796949B, the date of the authorized bulletin is 9, 10 and 2014, and the invention name is: the hot-dip galvanized steel sheet with the yield strength of more than or equal to 550MPa and the manufacturing method thereof are disclosed, and the hot-dip galvanized steel sheet comprises the following components in percentage by mass: 0.05-0.12% of C, less than or equal to 0.08% of Si, Mn: 0.3% -0.9%, Als: 0.020-0.060 percent, less than or equal to 0.03 percent of P, less than or equal to 0.03 percent of S, and the balance of Fe and inevitable impurities; the manufacturing method of the hot-dip galvanized steel plate with the yield strength of more than or equal to 550MPa comprises a steel plate CSP continuous casting and continuous rolling process, a steel plate pickling and cold rolling process and a steel plate continuous galvanizing process. The application reduces the grain size of ferrite and improves the strength of the product by reducing the CSP coiling temperature; the strength of the product is improved by controlling the reduction rate of acid rolling; the yield strength of the product is ensured by controlling the temperature, speed and hydrogen content of the galvanizing annealing. However, the hot dip galvanized steel sheet of the application adopts low carbon aluminum killed steel components, and the strength of the steel sheet is improved through the control of the annealing process, which also results in lower elongation, and the requirements of strength and elongation cannot be met at the same time.

Authorization notice number: CN104195434B, the date of authorized announcement is: 2016, 8, 17 days, the invention name is: the hot-dip galvanized high-strength steel with the tensile strength of 390MPa for the internal structural part of the sedan and the production method thereof, the steel of the application comprises the following chemical components in percentage by weight: c: 0.0027-0.0035%, Si: 0.071-0.095%, Mn: 0.78-0.95%, P: 0.060-0.075%, S is less than or equal to 0.003%, Als: 0.015 to 0.030%, Nb: 0.040-0.045%, Ti: 0.039-0.045%, B: 0.0008 to 0.0014, less than or equal to 0.003 percent of N, less than or equal to 0.002 percent of O, and the balance of Fe and inevitable impurities. The production method sequentially comprises the following steps: the method comprises the following steps of molten iron desulphurization, converter smelting, external refining, continuous casting, finishing, slab heating, hot continuous rolling, laminar cooling, coiling, acid washing, cold continuous rolling, continuous annealing and hot galvanizing, finishing and finishing. The steel has high-strength mechanical property, good formability, high content of favorable texture, good corrosion resistance and better surface quality requirement. However, in this application, the steel is strengthened by Si and P elements, and Si element is not good for the surface of the hot-dip galvanized steel sheet, and P element deteriorates the toughness of the steel sheet.

Disclosure of Invention

1. Technical problem to be solved by the invention

In view of the fact that the existing hot-dip galvanized steel sheet can not meet the requirements of high strength and elongation at the same time and can not adapt to the use requirements of high strength and high toughness; the invention provides a hot-dip galvanized steel sheet with the yield strength of 550MPa and a production method thereof, wherein the content of C element in the steel sheet is controlled, Mn, Ti, Nb, Cu and other elements are added to strengthen the steel sheet, P, S and other elements which are unfavorable to toughness are reduced as much as possible, Si and other elements which are unfavorable to surface quality are reduced, and the hot-dip galvanized steel sheet has high strength, high elongation and high plastic strain ratio and high surface quality requirements by matching with reasonable steel-making, hot-rolling, cold-rolling and hot-dip galvanizing processes; and through the control of the process, the strength of the produced steel plate cannot generate large fluctuation, the product yield is improved, and the cost is reduced.

2. Technical scheme

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

the invention relates to a hot-dip galvanized steel sheet with yield strength of 550MPa, which comprises the following chemical components in percentage by weight: 0.006-0.010% of C, less than or equal to 0.01% of Si, 0.10-0.30% of Mn, less than or equal to 0.015% of P, less than or equal to 0.040% of S, 0.005-0.070% of Als, 0.001-0.080% of Ti, 0.001-0.060% of Nb, less than or equal to 0.0030% of N, less than or equal to 0.0020% of O, 0.030-0.060% of Cu, 0.010-0.040% of Cr, and the balance of iron and other impurities.

Furthermore, the chemical composition ratio of the hot dip galvanized steel sheet satisfies the formula: ti + Nb is more than or equal to 0.050% and less than or equal to 0.120%.

The invention relates to a production method of a hot-dip galvanized steel sheet with a yield strength of 550MPa, which comprises the following steps:

firstly, pretreating molten iron;

step two, smelting in a converter and finely adjusting the alloy;

step three, refining in an RH furnace;

step four, continuous casting;

step five, hot rolling and cold rolling;

and step six, galvanizing.

Furthermore, in the first step, the pretreated molten iron is controlled to have the element S less than or equal to 0.0015 percent and the slag removing bright surface more than or equal to 80 percent.

Furthermore, in the second step, alloy auxiliary materials are added in sequence during tapping: pre-deoxidizing carbon powder, high-carbon ferromanganese, carburant, slag charge and aluminum iron, and deoxidizing the steel; and meanwhile, slag is blocked, and slag discharging and rephosphorization are prevented.

Furthermore, in the third step, RH adopts a light treatment process, and oxygen is blown in the early and middle stages according to the temperature and the oxygen level; and ensuring that the net circulation time is not less than 6min before breaking.

Furthermore, in the fourth step, the molten steel sedation time is not less than 20min, and the stopper rod argon blowing flow is controlled to be 4-6 NL/min; the target temperature of the tundish is controlled to be 15-30 ℃ above the liquidus temperature; casting at constant drawing speed under dynamic soft pressure, and controlling the fluctuation range of the liquid level within +/-3 mm; the discharging temperature of the casting blank is controlled to be 1200-1230 ℃.

Furthermore, in the fifth step, high-pressure descaling is carried out on an outlet and an inlet of the hot rolling rough rolling, an edge heater is arranged at an inlet of the hot rolling finish rolling, and high-pressure descaling water is fully opened at an outlet and an inlet of the finish rolling; the finishing temperature is controlled to be 870-910 ℃; the coiling temperature is controlled to be 580-630 ℃; the total rolling reduction rate of cold rolling is controlled to be 80-95 percent.

Furthermore, in the sixth step, the annealing temperature T and the time T of the RTF section are controlled to satisfy the relation of T/100 and 100/T to 4 of 1.3-1.3, and the finishing elongation L1 and the withdrawal and straightening elongation L2 are controlled to satisfy the relation of L1+ L2 to 1.2% of 0.6%.

Furthermore, the annealing temperature of the RTF section is controlled to be 600-630 ℃, and the time is 20-50 s; the finishing elongation L1 is controlled to be 0.5-1.0%, and the withdrawal and straightening elongation L2 is controlled to be 0.1-0.5%.

3. Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:

(1) according to the hot-dip galvanized steel sheet with the yield strength of 550MPa, the components and element percentage in the steel are optimally designed, so that the hot-dip galvanized steel sheet has high strength, high elongation and high plastic strain ratio, and the use of the hot-dip galvanized steel sheet under various conditions is met.

(2) The hot-dip galvanized steel sheet with the yield strength of 550MPa, disclosed by the invention, has the advantages that the ferrite grain size in the steel is refined and the strength and toughness of the steel are improved by controlling the content of C in the steel sheet, adding Mn, Cr, Al, Cu and other elements and controlling the content of the added elements; in addition, Ti and Nb are added into the steel, the contents of the two elements meet the formula of more than or equal to 0.050% and less than or equal to 0.120% of Ti + Nb, and the two elements are compounded, so that the ferrite grain size can be further refined, the strength and toughness of the steel plate can be improved, the strength and toughness of the steel can be well matched, and the requirements of yield strength and elongation are met.

(3) According to the production method of the hot-dip galvanized steel plate with the yield strength of 550MPa, the components, the component content and the specific production process of the steel plate are optimally designed, so that the strength and the toughness of the steel plate are effectively ensured, and the requirements of the yield strength and the elongation can be simultaneously met. The yield strength of the obtained galvanized steel sheet is more than or equal to 550MPa, the A50 elongation is more than or equal to 15%, and the galvanized steel sheet has better yield strength and elongation.

(4) According to the production method of the hot-dip galvanized steel sheet with the yield strength of 550MPa, the annealing temperature T and the annealing time T of the RTF section are controlled by controlling the galvanizing process, so that the annealing temperature T and the annealing time T meet the formula 1.3 and T/100 and T/4 respectively, the yield strength fluctuation of the steel caused by the double effects of the annealing temperature T and the annealing time T is reduced, the yield strength of the steel sheet is controlled between 550MPa and 650MPa, the fluctuation range of the yield strength is controlled within 100MPa, the product performance is stable, the product yield is high, and the production cost is reduced. Meanwhile, the finishing elongation rate L1 and the withdrawal and straightening elongation rate L2 are controlled to meet the formula of 0.6% to L1+ L2 to 1.2%, so that the stability of the elongation rate of the produced steel plate can be effectively ensured.

Drawings

FIG. 1 is a metallographic structure photograph showing a structure of a sample in example 1 of the present invention;

FIG. 2 is a metallographic structure photograph of comparative example 1 in the present invention;

FIG. 3 is a table of parameters of production processes of examples and comparative examples of the present invention;

FIG. 4 is a table showing mechanical properties of products of examples and comparative examples of the present invention.

Detailed Description

For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and examples.

The invention relates to a hot-dip galvanized steel sheet with yield strength of 550MPa, which comprises the following chemical components in percentage by weight: 0.006-0.010% of C, less than or equal to 0.01% of Si, 0.10-0.30% of Mn, less than or equal to 0.015% of P, less than or equal to 0.040% of S, 0.005-0.070% of Als, 0.001-0.080% of Ti, 0.001-0.060% of Nb, less than or equal to 0.0030% of N, less than or equal to 0.0020% of O, 0.030-0.060% of Cu, 0.010-0.040% of Cr, and the balance of iron and other impurities.

The invention optimizes the design of the components and element percentage in the steel and combines with reasonable steelmaking, hot rolling, cold rolling and hot galvanizing processes, so that the hot galvanized steel plate has high strength, high elongation and high plastic strain ratio, and the use of the hot galvanized steel plate under various conditions is met.

Specifically, the content of C element in the steel plate is controlled, Mn, Cr, Al, Cu and other elements are added, and the content of the added elements is controlled, so that the ferrite grain size in the steel is refined, and the strength of the steel is improved.

In addition, Ti and Nb are added into the steel, and the contents of the two elements meet the formula of 0.050% to 0.120% of Ti + Nb. At normal temperature, Ti and Nb are mostly present in steel in the form of carbides, nitrides, and carbonitrides. The two elements can improve the strength and the toughness, and are the most economical and effective method for improving the performance of the steel. By compounding the two elements, the ferrite grain size can be further refined, the strength and the toughness of the steel plate can be improved, the strength and the toughness of the steel can be well matched, and the requirements of yield strength and elongation are met.

According to the production method of the hot-dip galvanized steel sheet with the yield strength of 550MPa, the annealing temperature T and the annealing time T of the RTF section are controlled by controlling the galvanizing process, so that the annealing temperature T and the annealing time T meet the formula 1.3 and T/100 and T/4 respectively, the yield strength fluctuation of the steel caused by the double effects of the annealing temperature T and the annealing time T is reduced, the yield strength of the steel sheet is controlled between 550MPa and 650MPa, the fluctuation range of the yield strength is controlled within 100MPa, the product performance is stable, the product yield is high, and the production cost is reduced. Meanwhile, the finishing elongation rate L1 and the withdrawal and straightening elongation rate L2 are controlled to meet the formula of 0.6 percent to L1+ L2 to 1.2 percent, so that the stability of the elongation rate of the produced steel plate is ensured. By optimally designing the components, the component content and the specific production process of the steel plate, the strength and the toughness of the steel plate are effectively ensured, and the steel plate can simultaneously meet the requirements of yield strength and elongation. The yield strength of the obtained galvanized steel sheet is more than or equal to 550MPa, the A50 elongation is more than or equal to 15%, and the galvanized steel sheet has better yield strength and elongation.

The steel plate has the following functions of elements:

c: c is the most economical and effective solid-solution strengthening element for improving strength, and the content of C increases, the formed pearlite increases, and the strength increases, but the plasticity and formability of the steel decrease, and the weldability is not good. In order to ensure that the elongation percentage of the galvanized steel sheet meets the requirement while the strength of the galvanized steel sheet is improved, the inventor finally determines that the percentage content of C is controlled to be 0.006-0.010 percent through a large amount of research and summary, so that the strength of the steel sheet is improved, and the elongation percentage of the steel sheet cannot be reduced.

Si: the Si content is too high, the iron scale on the surface of the steel plate is not easy to remove, microcracks pressed by oxides are easily formed on the surface, and the microcracks are further used as crack sources to easily cause the steel plate to crack in the cold forming process, so the control range of the percentage content of Si is less than or equal to 0.01 percent.

Mn: mn can reduce the transformation temperature of austenite to ferrite (just can compensate the increase of the transformation temperature of austenite to ferrite caused by the reduction of the content of C element), expand the hot working temperature range and is beneficial to refining the grain size of ferrite, but the Mn content is too high, the Mn segregation degree of a casting blank is increased in the continuous casting process, the central part of the thickness of a steel plate is easy to form a pearlite or bainite banded structure, and the plasticity, the welding performance and the fatigue performance are not good.

P: p has a low diffusion rate in gamma-Fe and alpha-Fe, is easy to form segregation, and is unfavorable for the formability, low-temperature impact toughness and weldability of the steel plate. Therefore, the percentage content control range of P in the invention is less than or equal to 0.015 percent.

S: s is a harmful element under normal conditions, causes hot brittleness of steel, reduces ductility and toughness of the steel, causes cracks during forging and rolling, influences the surface quality of galvanized steel sheets, and requires the content of S to be as low as possible, so the S percentage content of the steel grade is controlled to be less than 0.010 percent.

Al: al is used as a main deoxidizer, and meanwhile, aluminum also has a certain effect on grain refinement. Aluminum has the disadvantage of affecting the hot workability, weldability and machinability of the steel.

Ti: ti is a strong deoxidizer in steel. It can make the internal structure of steel compact, refine grain force, raise strength of steel and improve welding property.

Nb: nb can refine grains, reduce the overheating sensitivity and the tempering brittleness of steel, improve the strength and improve the welding performance.

N: n can improve the strength, low-temperature toughness and weldability of steel and increase aging sensitivity. The percentage content control range of N in the invention is less than or equal to 0.0030 percent.

Cu: cu improves strength and toughness, but too high a copper content results in a significant reduction in plasticity.

Cr: cr is a strong carbide forming element, and is added as an alloy element, so that the activity of carbon in steel can be reduced, the strength of the steel is improved, and the hardenability of the steel is obviously improved.

The production method of the hot-dip galvanized steel sheet with the yield strength of 550MPa comprises the following specific steps:

firstly, pretreating molten iron: controlling the S content in the pretreated molten iron to be less than or equal to 0.0015 percent and the slag-removing bright surface to be more than or equal to 80 percent, and improving the purity of the molten steel.

Step two, smelting and fine-tuning the alloy in a converter: the dephosphorization of the converter is strengthened, and simultaneously the molten steel is deoxidized and alloyed (the adding sequence of alloy auxiliary materials is: pre-deoxidized carbon powder → high-carbon ferromanganese → carburant → slag → aluminum iron); strengthening slag stopping operation, preventing slag from being discharged and rephosphorized, modifying ladle top slag and reducing Al in steel₂O₃And (4) inclusion.

Step three, RH furnace refining: RH adopts light treatment process, if oxygen is required to be blown, oxygen is blown in the early and middle stages according to temperature and oxygen level; and ensuring that the net circulation time is not less than 6min before breaking. Reducing the generation of harmful impurities and improving the forming performance of the final product.

Step four, continuous casting: the molten steel sedation time is not less than 20min, and the stopper rod argon blowing flow is controlled to be 4-6 NL/min; the target temperature of the tundish is controlled to be 15-30 ℃ above the liquidus temperature; casting at constant drawing speed under dynamic soft pressure, and controlling the fluctuation range of the liquid level within +/-3 mm; and cleaning and checking the surface of the casting blank. If the tapping temperature is too low, the finishing temperature cannot be ensured; and the iron scale is pressed seriously during rolling due to the overhigh tapping temperature, so the tapping temperature of the casting blank is controlled to be 1200-1230 ℃.

Step five, hot rolling and cold rolling: during hot rolling, high-pressure descaling is carried out on an outlet and an inlet of hot rolling rough rolling, an edge heater is arranged at an inlet of hot rolling finish rolling, and high-pressure descaling water is fully opened at an outlet and an inlet of finish rolling. In order to avoid the rolling in the two-phase region, the finishing temperature is controlled to be 870-910 ℃. In order to ensure the mechanical property and the surface quality of the finished product, the coiling temperature is controlled to be 580-630 ℃. And during cold rolling, controlling the total rolling reduction rate of the cold rolling to be 80-95%.

Step six, galvanization: because the influence of the annealing temperature T and the annealing time T on the strength of the steel is in inverse correlation, the yield strength of the steel is reduced when the annealing temperature T is increased, the yield strength is also reduced when the annealing time T is prolonged, the fluctuation of the yield strength of the steel is increased under the double action of the annealing temperature T and the annealing time T, so that the annealing temperature T and the annealing time T of the steel need to be constrained and matched, the annealing time T is reduced when the annealing temperature T is higher, the annealing time T is prolonged when the annealing temperature T is lower, and the fluctuation of the mechanical property is reduced due to the matching of the annealing temperature T and the annealing time T. Therefore, the relation between the annealing temperature T and the time T is controlled to accord with the formula 1.3-T/100-T-4, specifically, the annealing temperature T of the RTF section is controlled to be 600-630 ℃, and the time T is 20-50 s. Meanwhile, in order to ensure the elongation of the steel plate, the finishing elongation L1 and the straightening elongation L2 satisfy the formula of 0.6% to L1+ L2 to 1.2%, specifically, the finishing elongation L1 is 0.5-1.0%, and the straightening elongation L2 is 0.1-0.5%.